1. Field of the Invention
The present seal assembly will function when pressure acts on it from two different directions. It is therefore sometimes referred to as a bi-directional seal or a dual energized hydroseal. The present invention can be used in a variety of different types of valves where a dual energized seal assembly is needed, as well as in cases where single-direction control is necessary.
2. Background of the Invention
The dual energized hydroseal includes a seal spool, two O-rings and two opposing seal cups. This bi-directional seal assembly can be used in a dirty fluid valve and a variety of other applications where a bi-directional seal assembly is needed, as well as in cases where a single direction seal assembly is necessary. For purposes of example, the dual energized hydroseal will be described in a dirty fluid valve, which is a type of cartridge valve frequently used in downhole tools. A plurality of dirty fluid valves are positioned in a downhole tool that is used for sampling wellbore fluids. A plurality of empty sample collection bottles are located in the downhole tool. When the tool is inserted in the wellbore, all of the dirty fluid valves are in the closed position as shown in FIG. 1. When the downhole tool reaches a depth that needs to be sampled, a pilot valve is pulsed, causing the seal carrier to slide the dual energized hydroseal assembly along opposing seal plates and open the supply port, as shown in FIG. 2. This allows wellbore fluids to enter the supply port of the dirty fluid valve and move through the longitudinal passageway of the valve and out the function port to a sample collection bottle. A plurality of sample collection bottles are often included in a single tool so that the wellbore may be sampled at different depths.
External pressures in a wellbore often exceed 20,000 psi absolute. After a sample has been collected, a pilot valve is pulsed, causing the seal carrier to move back to the close position as shown in FIG. 1. The pressure inside the sample collection bottle is the same as the pressure in the wellbore at the collection depth. As the downhole tool is brought back to the surface, external pressure drops to standard atmospheric pressure, but the pressure inside the sample collection bottle remains at wellbore pressure, which may be in excess of 20,000 psi absolute.
The present seal assembly will function when pressure acts on it from two different directions. The present invention can be used in a variety of different types of valves. When the seal assembly of the present invention is constructed, the O-rings are squeezed into position and/or compressed approximately 40%. The squeeze of the O-rings causes them to act as springs urging the seal cups into contact with the opposing seal plates. By contrast, O-ring manufacturers such as Parker generally recommend that O-rings be squeezed axially approximately 20%-30% for static seal designs. The present invention is a static seal design. Other O-ring manufacturers, such as Apple, recommend that O-rings be squeezed axially for static seal in the range of approximately 25%-38%. Squeezing the O-rings more than recommended by most manufacturers improves the function in the present invention. The O-rings in the present invention perform a dual function as both the spring and the seal. They act as a spring to force the seal cups into contact with the opposing seal plates, at lower pressures and they act as a seal at higher pressures.
U.S. Pat. No. 5,662,166 to Shammai, discloses an apparatus for maintaining at least downhole pressure of a fluid sample of upon retrieval from an earthbore. The Shammai device has a much more complex series of seal than the present invention. Further, the Shammi device does not have a dual-energized seal like the present invention.
U.S. Pat. No. 5,337,822 issued to Massie et al., discloses a wellfluid sampling tool. The Massie device maintains samples at the pressure at which they are obtained until they can be analyzed. The device does not, however, maintain this pressure by means of a dual-energized hydroseal. Rather, the device of Massey uses a hydraulically driven floating piston, powered by high-pressured gas such as nitrogen acting on another floating piston, to maintain sample pressure.
The seal assembly of the present invention uses two O-rings that are squeezed more than 38.5% causing them to act as springs urging the seal cups into sealing engagement at very low pressures with the seal plates and as seals at higher pressures. At higher pressure a seal is achieved because pressure on the rear of the seal cups forces them into sealing engagement with the opposing seal plates. The pressure forces act on the seal cups to achieve a tight metal to metal seal. The bi-directional seal assembly of the present invention is shown in a dirty fluid valve which is positioned in a downhole tool for sampling wellbore fluids. The seal assembly of the present invention can be used in a variety of other types of valves that require bi-directional seal assemblies and in other types of valves that only require a uni-directional seal.